This research will be done primarily at the Bose Institute in Calcutta, India in collaboration with Anuradha Lohia as an extension of NIH grant R01AI 53724. The human pathogen Entamoeba histolytica is responsible for causing amoebic dysentery and liver abscesses. Infection of the human gut is quickly followed by proliferation and multiplication of the parasite, which may then lead to colonic disease. We are interested in identifying molecular factors regulating cell proliferation in this protist parasite, in an effort to devise new strategies to prevent amoebiasis. The goal of the parent proposal is to identify novel amoebic virulence factors by microarray based transcriptional profiling. The FIRCA supplement is written with Prof. Anuradha Lohia who has been studying the regulation of cell cycle progression Entamoeba histolytica. Results from Anuradha's laboratory in India have shown that in E. histolytica genome reduplication may occur without cell division and single nuclei may contain several genome contents during the proliferative phase (Gangopadhyay et al, 1997a; Das and Lohia, 2002). Therefore, unlike most eukaryotes the cell cycle of E. histolytica does not appear to be controlled by known checkpoint surveillance mechanisms. It would be important therefore to identify a global profile of genes that regulate cell cycle progression in E. histolytica. In this proposal we plan to use dsRNA interference (Kaur and Lohia, 2004) to down-regulate cell cycle homologues- Eh Cdks and cyclins, followed by transcriptional profiling using microarrays in order to identify groups of genes controlled by CDKs and cyclins in E. histolytica. This work has important implications for identifying novel aspects of cell cycle control in E. histolytica. .Additionally, this project is an ideal collaborative environment in which a main goal is technology transfer (use and anlaysis of microarray data) to the Lohia lab in India. Arrays as a post-genomic tools are powerful yet highly specialized, thus the "hands-on" use of this application by Lohia's group is an important component of this work.